Head stack assembly installation system for a disc drive

ABSTRACT

A head stack assembly installation system with a frame supporting a head stack installation tool including a robotic assembly supporting a measurement assembly communicating with a computer hosting an installation software program. The robotic assembly picks and places the head stack assembly into the head disc assembly and the measurement assembly collects and communicates process positions and force parameters to the computer, the computer calculating distance and force data. The installation software program directs and controls enactment of process steps followed by the head stack installation tool to install or abort installation of the head stack assembly based on the position and force data.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/641,695 filed Aug. 18, 2000, now abandoned which claims priority toU.S. Provisional Application No. 60/150,138 filed Aug. 20, 1999.

FIELD OF THE INVENTION

The present invention relates generally to the field of disc drive datastorage devices, and more particularly, but not by way of limitation, toan automated assembly of a head-disc assembly of a disc drive, whichincludes a head stack assembly installation system.

BACKGROUND

Modern hard disc drives are commonly used in a multitude of computerenvironments, ranging from super computers through notebook computers,to store large amounts of data in a form that can be made readilyavailable to a user. Typically, a disc drive comprises one or moremagnetic discs that are rotated by a spindle motor at a constant highspeed. The surface of each disc is a data recording surface divided intoa series of generally concentric recording tracks radially spaced acrossa band having an inner diameter and an outer diameter. The data tracksextend around the disc and store data within the tracks on the discsurfaces in the form of magnetic flux transitions. The flux transitionsare induced by an array of transducers, otherwise commonly calledread/write heads. Typically, each data track is divided into a number ofdata sectors that store fixed sized data blocks.

The read/write head includes an interactive element such as a magnetictransducer, which senses the magnetic transitions on a selected datatrack to read the data stored on the track. Alternatively, theread/write head transmits an electrical signal that induces magnetictransitions on the selected data track to write data to the track.

As is known in the art, each read/write head is mounted to a rotaryactuator arm and is selectively positionable by the actuator arm over aselected data track of the disc to either read data from or write datato the selected data track. The read/write head includes a sliderassembly having an air-bearing surface that causes the read/write headto fly above the disc surface. The air bearing is developed as a resultof load forces applied to the read/write head by a load arm interactingwith air currents that are produced by rotation of the disc.

Typically, a plurality of open-center discs and open-centered spacerrings are alternately stacked on the hub of a spindle motor, followed bythe attachment of a clampring to form a disc pack or disc stack. Thehub, defining the core of the stack, serves to align the discs andspacer rings around a common centerline. Movement of the discs andspacer rings is typically constrained by a compressive load maintainedby the clampring. The read/write heads mounted on a complementary stackof actuator arms, which compose an actuator assembly, commonly called anE-block, accesses the surfaces of the stacked discs of the disc pack.The E-block also generally includes read/write head wires which conductelectrical signals from the read/write heads to a flex circuit which, inturn, conducts the electrical signals to a printed circuit boardassembly (PCB). When the E-block is merged with the disc pack into abase deck and a cover is attached to the base deck a head-disc assembly(HDA) is formed. For a general discussion of E-block assemblytechniques, see U.S. Pat. No. 5,404,636 entitled METHOD OF ASSEMBLING ADISC DRIVE ACTUATOR issued Apr. 11, 1995 to Stefansky et al., assignedto the assignee of the present invention.

The head-disc assembly (HDA) of a disc drive is typically assembled in aclean room environment. The need for maintaining a clean roomenvironment (free of contaminants of about 0.3 micron and larger) is toensure the head-disc interface remains unencumbered and damage free. Theslightest damage to the surface of a disc or read/write head can resultin a catastrophic failure of the disc drive. The primary causes ofcatastrophic failure, particularly read/write head crashes (anon-recoverable, catastrophic failure of the disc drive), are generallycharacterized as contamination, exposure to mechanically induced shock,and non-shock induced damage. The source of non-shock induced damage istypically traced to the assembly process, and generally sterns fromhandling damage sustained by the disc drive during the assembly process.

Several factors that bear particularly on the problem of assemblyprocess induced damage are the physical size of the disc drive, thespacing of the components, the recording densities sought to be achievedand the level of precision to be maintained during the assembly process.The high levels of precision required by the assembly process arenecessary to attain the operational tolerances required by the discdrive. The rigorous operational tolerances are in response to marketdemands that have driven the need to decrease the physical size of discdrive while simultaneously increasing disc drive storage capacity andperformance characteristics.

Demands on disc drive mechanical components and assembly procedures havebecome increasingly more critical in order to support capability andsize in the face of these new market demands. Part-to-part variation incritical functional attributes in the magnitude of a micro-inch canresult in disc drive failures. Additionally, as disc drive designscontinue to decrease in size, smaller read/write heads, thinnersubstrates, longer and thinner actuator arms, and thinner gimbalassemblies will continue to be incorporated into the drives. This trendsignificantly increases the need to improve the assembly processes toprotect the read/write heads and discs from damage resulting fromincidental contact between mating components. The aforementioned factorsresultantly increase the difficulty of assembling disc drives. As theassembly process becomes more difficult, the need to invent new tools,methods and control systems to deal with the emerging complexitiespresents unique problems in need of solutions.

Coupled with the size and performance improvement demands is the factorof further market driven-requirements for ever increasing fault treeperformance. The progression of continually decreasing disc thicknessand disc spacing, together with increasing track density and increasingnumbers of discs in the disc pack, has resulted in a demand for tools,methods and control systems of ever increasing sophistication. A resultof the growth in demand for sophisticated assembling equipment has beena decreasing number of assembly tasks involving direct operatorintervention. Many of the tasks involved in modern assembly methods arebeyond the capability of operators to reliably and repeatedly perform,further driving the need for automation equipment and tools.

In addition to the difficulties faced in assembling modern disc drivesof high capacity and complex, physical product performance requirementshave dictated the need to develop new process technologies to ensurecompliance with operating specifications. The primary factors drivingmore stringent demands on the mechanical components and the assemblyprocess are the continually increasing areal densities and data transferrates of the disc drives.

The continuing trend in the disc drive industry is to develop productswith ever increasing areal densities, decreasing access times andincreasing rotational speeds. The combination of these factors, placegreater demands on the ability of modern servo systems to control theposition of read/write heads relative to data tracks. The ability toassemble HDAs nominally free from the effects caused by unequal loadforces on the read/write heads, disc pack imbalance or one of thecomponents of runout, velocity and acceleration (commonly referred to asRVA) posses a significant challenge as track densities increase. Thecomponents of RVA are: disc runout (a measure of the motion of the discalong the longitudinal axis of the motor as it rotates); velocity (ameasure of variations in linear speed of the disc pack across thesurface of the disc); and acceleration (a measure of the relativeflatness of the discs in the disc pack).

One cause of unequal load forces on the read/write heads stems frommisalignment of the head stack assembly during assembly of the HDA.Misalignment of the head stack assembly causes the fly-height of theindividual read/write heads to deviate from optimum, causing an increasein the distance between the disc and the head for some surfaces anddecreasing the distance for others. If the deviation is substantial;head/disc contact occurs that can lead to head crashes. For less severedeviations in fly heights, soft read errors often develop. If the softerrors are detected in the test process, the HDA is returned to theclean room for rework, exposing the HDA to handling damage. If the softerrors go undetected during the test process and develop duringoperation in the field, disc drive performance denigrates, write faultsmay be reported and reliability of the disc drive suffers. The abilityto control the alignment of the head stack assembly derives from theability to precisely control the installation of the head stack assemblyinto the HDA.

By design, a disc drive typically has a discreet threshold level ofresistance to withstand rotationally induced noise and instability,below which the servo system is not impaired. Also, a fixed range ofload forces must be maintained on the read/write head to ensure properfly height for data exchange. The operating performance of the discdrive servo system is affected by mechanical factors beyond the effectsof mechanically induced read/write head oscillation from disc surfaceanomalies. Errors are traceable to disc pack imbalance and RVA noisesources. Even with improved approaches to the generation of positionerror signals in the disc drive servo system, the ability of the systemto deal with such issues is finite. The limits of the; servo systemcapability to reliably control the position of the read/write headrelative to the data track must not be consumed by the noise present inthe HDA resulting from the assembly process. Consumption of theavailable margin by the assembly process leaves no margin in the systemto accommodate changes in the disc drive attributes over the life of theproduct. An inability to accommodate changes in the disc driveattributes leads to field failures and an overall loss in productreliability, a detrimental impact to product market position.

Thus, in general, there is a need for an improved approach to discdrive-assembling technology to minimize the potential of damage duringassembly, to produce product that is design compliant and reliable, andto minimize mechanically induced system noise. More particularly, thereis a need for a head stack assembly installation system controlling theinstallation of the head stack assembly into an HDA of a disc drive.

SUMMARY OF THE INVENTION

The present invention provides a head stack assembly installation systemwith a head stack installation tool electronically communicating with acomputer that has an active installation software program directing andcontrolling process steps enacted by the head stack installation tool toinstall a head stack assembly into a head disc assembly of a disc drive.The head stack installation tool provides a nesting position foraligning and staging the head stack assembly prior to installation intothe lead disc assembly, an installation position for locating andsecuring the head disc assembly while awaiting installation of the headstack assembly, a robotic assembly and a measurement assembly. Therobotic assembly picks and places the head stack assembly into the headdisc and the measurement assembly collects and communicates processposition and force parameters to the computer for use by the computer incalculating distance and force data. The active installation softwareprogram directs and controls enactment of process steps followed by thehead stack installation tool by directing the computer to executeinstallation software program steps based on the position and force datacalculated by the computer.

These and other features and advantages which characterize the presentinvention will be apparent from a reading of the following detaileddescription and a review of the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cutaway top view of a disc drive of the typeassembled by the head stack assembly installation system of the presentinvention.

FIG. 2 is a partially cutaway top view of a basedeck assembly for thedisc drive of FIG. 1.

FIG. 3 is an elevational view of the flex connector body with attachedflex circuit and actuator assembly serial number for the disc drive ofFIG. 1.

FIG. 4 is a partial cutaway elevational and partial cross-sectional viewof the disc drive of FIG. 1.

FIG. 5 is a plan view of the actuator assembly of the disc drive of FIG.1.

FIG. 6 is a partial cutaway elevational view of the actuator assembly ofthe disc drive of FIG. 1.

FIG. 7 is a partial cutaway perspective view of the head stack assemblyinstallation system of the present invention.

FIG. 8 is a perspective view of an end effector assembly of the headstack assembly installation system of FIG. 7.

FIG. 9 is a cross-sectional, partial cutaway view of radially disposedpositionable gripper sections of the end effector of FIG. 8.

FIG. 10 is a flow chart of system hardware communication for the headstack assembly installation system of FIG. 7.

FIG. 11 is a flow chart for logic of main process steps of aninstallation software program of the head stack assembly installationsystem of FIG. 7.

FIG. 12 is a flow chart for logic of head stack assembly installationprocess steps of the installation software program of the head stackassembly installation system of FIG. 7.

FIG. 13 is a flow chart for logic of head stack assembly installationanalysis process steps of the installation software program of the headstack assembly installation system of FIG. 7.

FIG. 14 is a diagram showing a family of empirically derived mechanicalresistance thresholds.

DETAILED DESCRIPTION

Referring to the drawings in general, and more particularly to FIG. 1,shown therein is a top view of a disc drive 100 constructed inaccordance with the present invention. The disc drive 100 includes abasedeck 102 that has several fastener receptacles 104, the basedeck 102supporting various disc drive components, and a top cover 106 (shown inpart), with several mounting apertures (not separately shown), securedto the basedeck 102 by top cover fasteners 108. The installed top cover106 together with the basedeck 102 provides a sealed internalenvironment for the disc drive 100. Numerous details of and variationsfor the construction of the disc drive 100 are not included in thefollowing description as such are well known to those skilled in the artand are believed to be unnecessary for the purpose of describing thepresent invention.

Mounted to the basedeck 102 is a ramp load snubber assembly 110 securedto the basedeck 102 by a fastener 112, and a spindle motor 114 with atop cover attachment aperture 116. The spindle motor 114 supportsseveral discs 118 for rotation at a constant high speed, the discs 118mounted on a spindle motor hub 120 that are secured by a clampring 122with clampring fasteners 124. In addition to providing support for thestacked discs 118, the spindle motor hub 120 also provides a timing mark126 used during the assembly process to reference the angular locationof a source of rotational imbalance. Adjacent the discs 118 is anactuator assembly 128 (also referred to as an “E-block” or a head stackassembly (HSA)) which pivots about a bearing assembly 130 in a rotaryfashion. The bearing assembly supports a beveled pick and place member132 that serves as a tooling grip during assembly operations. The HSA128 includes actuator arms 134 (only one shown) that support load arms136. Each load arm 136 in turn supports read/write heads 138, with eachof the read/write heads 138 corresponding to a surface of one of thediscs 118. As mentioned, each of the discs 118 has a data recordingsurface divided into concentric circular data tracks 140 (only oneshown), and the read/write heads 138 are positionably located over datatracks to read data from, or write data to, the tracks.

The HSA 128 is controllably positioned by a voice coil motor assembly(VCM) 142, comprising an actuator coil 144 immersed in the magneticfield generated by a magnet assembly 146. A magnetically permeable fluxpath is provided by a steel plate 148 (also called a top pole piece)mounted above the actuator coil 144 to complete the magnetic circuit ofthe VCM 142.

When controlled DC current is passed through the actuator coil 144, anelectromagnetic field is setup, which interacts with the magneticcircuit of the VCM 142 to cause the actuator coil 144 to move relativeto the magnet assembly 146 in accordance with the well-known Lorentzrelationship. As the actuator coil 144 moves, the HSA 128 pivots aboutthe bearing assembly 130, causing the heads 138 to move over thesurfaces of the discs 118 thereby allowing the heads 138 to interactwith the data tracks 140 of the discs 118. When the disc drive 100 isturned off, the VCM 142 parks the HSA 128 on the ramp load snubberassembly 110 to avoid shock induced contact between the read/write heads138 and the discs 118.

To provide the requisite electrical conduction paths between theread/write heads 138 and disc drive read/write circuitry (not shown),read/write head wires (not shown) are affixed to a read/write flexcircuit 150. Next the read/write flex 150 is routed from the load arms136 along the actuator arms 134 and into a flex circuit containmentchannel 152 and on to a flex connector body 154. The flex connector body154 supports the flex circuit 150 during passage of the read/write flexcircuit 150 through the basedeck 102 and into-electrical communication adisc drive printed circuit board assembly (PCBA) (not shown) mounted tothe underside of the basedeck 102. The flex circuit containment channel152 also supports read/write signal circuitry 156 used to conditionread/write signals passed between the read/write circuitry (not shown)and the read/write heads 138. The disc drive PCBA provides the discdrive read/write circuitry, which controls the operation of the heads138, as well as other interface and control circuitry for the disc drive100.

To maintain the sealed internal environment for the disc drive 100, aseal gasket 158 is molded on to the top cover 106. Top cover 106 has amultitude of gasket attachment apertures 160 through, which gasketmaterial flows during the gasket molding process. A continuum ofsymmetrically formed gasket material is disposed on both the top andbottom surfaces of the top cover 106 and injected through the apertures160. During the cure process, the gasket material injected into thegasket attachment apertures 160 bonds the portion of the seal gasketadjacent the top surface of the top cover 106 to the portion of the sealgasket adjacent the bottom portion of the top cover 106, thereby sealingthe gasket attachment apertures 160 and forming the seal gasket 158. Agasket material found to be useful for this application is “Fluorel” bythe 3M Company, and more specifically, 3M “Fluorel”, FE-5621Q.

The disc drive 100 has two primary assemblies, the PCBA (not shown) anda head disc assembly (RDA) 162 attached to the PCBA. The RDA 162typically contains the mechanically active assemblies and components ofthe disc drive 100. Typically included within the HDA 162 are the HSA128, the VCM 142 and a disc stack 164 sustained within the sealedenvironment created when the top cover 106 supporting the seal gasket158 is secured to the basedeck 102 by fasteners 108. The disc stack 164is formed by stacking discs 118, interleaved with spacer rings (notshown), on the spindle hub 120 of the spindle motor 114 and securing thestack with the clampring 122 and fasteners 124.

During operation of the disc drive 100, spinning discs 118 generateairflow consistent with the direction of rotation of the spinning discs118. To reduce chances of a catastrophic failure of the disc drive 100caused by particulate contamination internal to the HDA 162, an airfilter 166 is provided internal to the HDA 162 to trap airborneparticulate either present following assembly or generated duringoperation of the disc drive 100.

FIG. 2 shows a basedeck assembly 168 to include the basedeck 102, thedisc pack assembly 168, the air filter 166, a bottom pole piece 170supporting a rare earth magnet 172 and a head stack assembly post 174supporting a removably attached tolerance ring 176. The bottom polepiece 170, with the rare earth magnet 172, together with the top polepieces 148, supporting a second rare earth magnet (not shown), form themagnet assembly 146 and the actuator coil 144 collectively form the VCM142. The basedeck assembly 168 together with an installed HSA 128,magnet assembly 146 and top cover 106 combined to form the HDA 162 ofFIG. 1.

FIG. 3 shows the flex connector body 154 with the attached flex circuit150 supporting a machine-readable head stack assembly serial number 178.In a preferred embodiment machine-readable head stack assembly serialnumber 178 is a barcode but could also be characters capable of beingoptically recognized using optical character recognition software (OCR)or other comparable coding methodologies. The serial number 178represents the physical characteristics for a particular HSA 128 thatincludes information such as the number and type of read/write heads 138the HSA 128 contains, the type of bearing assembly 130 or the type ofactuator coil 144 supported by the HSA 128.

FIG. 4 shows the disc drive 100 with a machine-readable head discassembly serial number 180. Also shown by FIG. 4 is the mechanicalinterface between the bearing assembly 130 of the HSA 128 and thetolerance ring 176 removably attached to the head stack assembly post174. The bearing assembly 130 includes the beveled pick and place member132, and an inner race 182 separated by a bearing 184 from an outer race186. During installation of the HSA 128 into the basedeck assembly 168the inner race 182 of the bearing assembly 130 forcefully engages thetolerance ring 176 as the HSA 128 is pressed onto the tolerance ring 176through application of a compressive load on the HSA 128.

FIG. 5 shows a tooling hole 188 provided in the actuator arms 134 tosupport the load arms 136. Typically, the load arms 136 are affixed tothe actuator arms 134 through a process referred to as swaging. Theswaging process normally involves alignment of the load arms 136 withthe actuator arms 134 and passage of a swage tool through the toolinghole 188. A tooling hole 190 is provided to facilitate alignment andcontainment of an actuator body 192 during assembly of the HSA 128,including the swaging process.

Actuator coil support arms 194 support the actuator coil 144 of the HSA128 and serve as reference surfaces, along with tooling hole 190, foralignment of the HSA 128 in preparation for installation of the HSA 128into head disc assembly 162. Additionally, FIG. 5 shows actuator coilleads 196 electrically communicating with the read/write flex circuit150, the actuator coil leads 196 conduct current from the read/writeflex circuit 150 to the actuator coil 144, facilitating operation of theVCM 142.

To initiate the process of installing the HSA 128 onto the tolerancering 176, an operator completes a series of inspection and preparationsteps. The operator first checks the flex connections (not separatelyshown) and the bearing assembly 130 to assure the HSA 128 is intact.Next the operator manually removes a shipping constraint (not shown),used to protect the HSA 128 during shipment, and adjusts the head stackassembly installation comb 198 to complete the preparation andinspection steps.

FIG. 6 shows the relationship between the various members and componentsof the HSA 128. The majority of mass of the HSA 128 is concentratedaround the axis of rotation of the bearing assembly 130 and is made upby the actuator body 192 and the bearing assembly 130. The actuator body192 supports the actuator coil support arms 194, the actuator arms 134and bearing assembly 130. The beveled pick and place member 132 issupported by the bearing assembly 130 and protrudes about the top plainof the actuator body 192. The beveled pick and place member 132 providesa grip for handling the HSA 128 during installation of the HSA 128 intothe basedeck assembly 168 of the HDA 162 of the disc drive 100.

FIG. 7 shows a head stack assembly installation system 200 with a frame202 supporting a head stack assembly installation tool 204 and acomputer 206. For a preferred embodiment, the computer 206 is shownadjacent the head stack assembly installation tool 204 and supported bythe frame 202. However, the head stack assembly installation tool 204and the computer 206 need not be proximately located, one to the other.Electronic communication between the head stack assembly installationtool 204 and the computer 206 is sufficient to operate the head stackassembly installation tool 204 during installation of the HSA 128 intothe HDA 162.

The computer 206 is a host for an installation software program (notshown) that has installation software program steps. The computer 206 isused to calculate position and force data from position and forceparameter measurements gathered by the head stack assembly installationtool 204 during the process of installing the actuator assembly 128 intothe basedeck assembly 168 of the HDA 162. The installation softwareprogram directs and controls process steps executed by the head stackassembly installation tool 204, based-on the position and force datacalculated by the computer 206 from the position and force parametermeasurements gathered by the head stack assembly installation tool 204.

The head stack installation tool 204 has a main plate 208 that providesa nesting position 210, an installation position 212 and a roboticassembly 214. The nesting position 210 provides a tooling pin 216 thatcommunicates with the tooling hole 190 of the HSA 128; a connector nest218, which cradles and aligns the flex connector body 154 of the HSA 128with the actuator body 192 for installation of the HSA 128 into the HDA162; and head stack assembly alignment pins 220 that interface with theactuator coil support arms 194 to maintain the HSA 128 in apredetermined position prior to installation of the HSA 128 into thebasedeck assembly 168. The installation position 212 aligns the basedcckassembly 168 of the HDA 162 for installation of the HSA 128 into thebasedeck assembly 168. Adjacent the installation position 212 is a liftand locate assembly 222 that lifts the basedeck assembly 168 from aconveyor (not shown) and locates the basedeck assembly 168 within theinstallation position 212. Additionally, the main plate 208 supports ahead stack assembly scanner head 224 adjacent the nesting position 210to read the machine readable head stack assembly serial number 178; ahead disc assembly scanner head 226 adjacent the installation position212 to read the machine readable head disc assembly serial number 180; ahead stack assembly present sensor 228 adjacent the head stack assemblyalignment pins 220 to detect the presence of HSA 128 in the nestingposition 210; and a head disc assembly present sensor 230 adjacent theinstallation position 212 to detect the presence of the basedeckassembly 168 within the installation position 212.

The robotic assembly 214 has an end effector assembly 232 supported by avertical slide assembly 234, which in turn is supported by a horizontalslide assembly 236 that is directly supported by the main plate 208. Theposition of the vertical slide assembly 234 during the operation of thehead stack assembly installation system 200 is reported to the computer206 by a vertical slide digital sensor 238 located adjacent the verticalslide 234. The position of the horizontal slide assembly 236, during theoperation of the head stack assembly installation system 200, isreported to the computer 206 by a horizontal slide digital sensor 240positioned adjacent the horizontal slide 236. The end effector assembly232 uses the beveled pick and place member 132 of the HSA 128 to gripthe HSA 128 for installation onto the tolerance ring 176. The endeffector assembly 232 also has a pair of opposing positionable flexconnector grippers 242 configured to communicate with the flex connectorbody 154. A pair of opposing positionable flex connector grippers 242maintain alignment of the flex connector body 154 in relation to theactuator body 192 while the robotic assembly 214 is pressing the HSA 128onto the tolerance ring 176 during the process of installing the HSA 128into the basedeck assembly 168 of the HDA 162. A pneumatic cylinderhousing 244 supports the pair of opposing positionable flex connectorgrippers 242 as well as supporting a pneumatic cylinder (not shown) usedto operate the pair of opposing positionable flex connector grippers242.

As shown in FIG. 7, a communication interface-electronics assembly 246is mounted internal to the computer to 206. However, like the computer206 itself, the communication interface electronics assembly 246 neednot be proximately located to the computer 206, but rather, electroniccommunication between the communication interface electronics assembly246 and the computer 206 is sufficient to operate the head stackassembly installation tool 204 during installation of the HSA 128 intothe HDA 162. The communication interface electronics assembly 246cooperates with a measurement assembly 247 that includes a radialdisplacement potentiometer 248, a linear variable differentialtransformer 250 (LVDT), and a load cell 252. The radial displacementpotentiometer 248 is supported by the end effector assembly 232 andelectronically communicates with the communication interface electronicsassembly 246 during the process of installing the HSA 128 into thebasedeck assembly 168. The radial displacement potentiometer 248measures position parameters of the gripping action of the end effectorassembly 232 during installation process, and reports the measurementsto the computer 206 through the communications interface electronicsassembly 246. The LVDT 250 is supported by the vertical slide assembly234 and electronically communicates with the communication interfaceelectronics assembly 246 during the installation process. The LVDT 250measures parameters of vertical distance traveled by the vertical slide234 relative to the head stack assembly post 174 and reports themeasured parameters to the computer 206. The load cell 252 is supportedby the end effector assembly 232 and electronically communicates withthe communication interface electronics assembly 246 during the HSA 128to HDA 162 installation process. The load cell 252 measures parametersof mechanical resistance between the tolerance ring 176 and HSA 128,while the HSA 128 is being pressed onto the tolerance ring 176 toinstall the HSA 128 into the HDA 162.

FIG. 8 shows a gripper 254 of the end effector 232. Included in thegripper 254 is a radially disposed positionable gripper section 258linked to operate in unison and attached to a gripper housing 260. Eachgripper section 258 supports a gripper finger 262 that is shaped toconform to the slope of the external surface of the beveled pick andplace member 132. Each of the radially disposed positionable grippersections 258 is coupled to the potentiometer 248 by a potentiometercoupling arm 264.

A push pad (also referred to as a “centering post”) 266 is attached tothe gripper housing 260 and circumvented by the radially disposedpositionable gripper sections 258. The radially disposed positionablegripper sections 258 move toward the push pad 266 contacting beveledpick and place member 132 to align the HSA 128 to the end effectorassembly 232. Alignment of the HSA 128 to the end effector assembly 232includes alignment of the top inner race 182 to the push pad 266. Duringthe installation process the gripper lingers 262 remain in contact withthe beveled pick and place member 132 until contact is establishedbetween the HSA 128 and the head stack assembly post 174. Uponmeasurement of initial contact between the HSA 128 and the HDA 162, andreporting of that measured contact to the computer 206 by the load cell252, the radially disposed positionable gripper sections 258 disengagecontact with the beveled pick and place member 132. The push pad 266remains in contact with the inner race of the bearing assembly 130 totransfer the compressive load delivered by the end effector assembly 232to the HSA 128 during the process of pressing the HSA 128 onto thetolerance ring 176 of the HDA 162. Retracting the radially disposedpositionable gripper sections 258 from contact with the beveled pick andplace member 132 during the process of pressing the HSA 128 intoposition reduces the chances of the bearing 184 being damaged duringinstallation process.

FIG. 9 shows the interaction between the gripper fingers 262, the pushpad 266 and the beveled pick and place member 132. The gripper fingers262 provide a slope surface 268 that conforms to the slope of the outersurface of the beveled pick and place member 132 while the push pad 266provides a shouldered outer diameter 270 that is inserted into the innerrace of the pick and place member 132. When activated to engage the HSA128, the radially disposed positionable gripper sections 258 contact theouter surface of the bevel pick and place member 132 and align the HSA128 to the end effector assembly 232 by positioning the inner surface ofthe pick and place member 132 into contact with the outer diameter 270of the push pad 266.

FIG. 10 shows a central processing unit 272 (CPU) electronicallycommunicating with recordable media 274. The recordable media 274 holdsan installation software program (not separately shown) that hasinstallation software program steps to carry out the assembly hereindescribed. The term electronically communicating or in electroniccommunication does not necessarily mean that the two devices engaging inthe communication are physically connected. The term includes devicesthat are physically connected and devices that are electronicallyconnected via networking links such as infrared communication,radio-frequency communication or through the internet via satellitecommunication. For example, the recordable media 274 may be located inone country, for example the United States, and the CPU 272 could belocated in a different country, for example Ireland. The two devices,the CPU 272 and the recordable media 274, are each elements of the headstack assembly installation system 200, dependent on each other for thefunctioning of the head stack assembly installation system 200, butneither is in direct physical contact with the other. They are however,linked, one to the other, electronically as portions of the head stackassembly installation station 200. FIG. 10 also shows the CPU 272 inelectronic communication with a volatile memory 276 (also referred toherewith in as random access memory or RAM), a head stack assemblyserial number data base 278 and a head disc assembly serial number database 280.

The CPU 272 electronically communicates with the recordable media 274 toupload the installation software program into the RAM 276 prior toexecution of the installation process. During the installation processthe installation software operates out of the RAM 276. In addition tocontaining an active version of the installation software program theRAM 276 also temporarily stores information communicated to the computer206 from the communication interface electronics assembly 246. Thestored information includes a head stack present signal (not shown),detected by the head stack digital sensor 228, a head disc presentsignal (not shown), detected by the head disc assembly present digitalsensor 230, a value (not shown) representing the head stack assemblyserial number 178, provided by the head stack assembly scanner head 224and a value (not shown) presenting the head disc assembly serial number180, provided by the head disc assembly scanner head 226. Duringoperation of the head stack assembly installation system 200 additionaldata regarding position and force parameters encountered by the HSA 128during the installation process as well as position data for theradially disposed positionable gripper sections 258, the vertical slideassembly 234 and the horizontal slide assembly 236 are gathered andwritten to the RAM 276 on a real-time basis. The position of thehorizontal slide assembly 236 is monitored and reported to thecommunication interface electronics 246 by the linear horizontal slidedigital sensor 240, the position of the vertical slide assembly 234 ismonitored and reported to the communication interface electronics 246 bythe linear vertical slide digital sensor 238, while position data forthe gripper sections 258 is continually monitored by the radialdisplacement potentiometer 248. The position and force parametermeasurements encountered by the HSA 128 while being pressed onto thetolerance ring 176 are made and supplied to the RAM 267 by the linearvariable differential transformer 250 and the load cell 252respectively.

Two additional elements of the head stack installation system 200 areshown by FIG. 10. In electronic communication with the CPU 272 are theHSA serial number data base 278 and the HDA serial number data base 280,the HSA serial number data base 278 containing the physicalcharacteristics of each HSA 128 available for installation into each HDA164, while the HDA serial number data base 280 contains the physicalcharacteristics of each HDA 164 available for receipt of the HSA 128.Prior to joining each available HSA 128 with each available HDA 164, theinstallation software program instructs the CPU 272 to read the serialnumber 178 of the HSA 128 from RAM 276, query the HSA serial number database 278 and retrieve the physical characteristics information containedwithin the HSA serial number data base 278 for the HSA 128 serial numberread from the RAM 276. The installation software program then instructsthe CPU 272 to read the serial number 180 from RAM 276, query the HDAserial number data base 280 and retrieve the physical characteristicsinformation contained within the HDA serial number data base 280 for theHDA 164 serial number read from the RAM 276. The software installationprogram then instructs the CPU 272 to compare the physicalcharacteristics of the HDA 164 and the HSA 128 to one another, to ensurecompatibility prior to proceeding with the installation of the HSA 128into the HDA 164.

FIG. 11 shows a main process decision flow 300 utilized by theinstallation software program to grip the HSA 128 in preparation forinstallation of the HSA 128 into the HDA 164 of the disc drive 100. Oncea start step 302 of the installation software program steps isinitialized, three decision steps follow. The first decision step, HDAin position 304, verifies the presence of the HDA 164 within theinstallation position 212 of the main plate 208. The second decisionstep, HSA positioned in the nest 306, verifies the presence of HSA 128in the nesting position 212 of the main plate 208 and the third decisionstep, HSA serial number entered 308, verifies the presence of the serialnumber 178 within the RAM 276.

The main process decision flow 300 shows the installation softwareprogram instructs the robotic assembly 214 to grip the HSA 128 andproceed to predefined process steps install HSA decision flow 320 (ofFIG. 12), provided responses of the three decision steps are affirmativealong with an affirmative response from a decision step HSA and HDAcompatible 310. In addition to the specifically identified decisionsteps, the main process decision flow 300 shows the decision loopsentered into by the installation software program if a non affirmativeresponse is encountered from one of the specifically identified decisionsteps. The software installation program remains in the decision loopuntil the installation software program, from that decision loop,receives an affirmative response.

FIG. 12 shows the install HSA decision flow 320 of the installationsoftware program utilized by the installation software program to engagethe tolerance ring 176 with the HSA 128. A start step 322 is the firstinstallation software program step of the install HSA decision flow 320.There are two primary decision steps involved in the install HSAdecision flow 320. The first, a HSA engaged post 324, initiates step 326upon successful engagement of the head stack assembly post 174 with theHSA 128. Installation software program step 326 directs the actions ofreleasing the radially disposed positionable gripper sections 258 fromcontact with the beveled pick and place member 132, applying acompressive load on the HSA 128 with the robotic assembly 214, andcollecting force and distance parameters from the load cell 252 and theLVDT 250 respectively. Upon successful completion of the second decisionstep, slide stopped moving 328, the installation software programinitiates step 330, an action of raising the vertical slide 234 todiscontinue application of the compressive load on the HSA 128 and toproceed to an analyze force and position data-decision flow 340 (of FIG.13), another predefined sequence of process steps of the installationsoftware program.

The install HSA decision flow 320 shows the decision loops entered intoby the installation software program should a non affirmative responsebe a result of one of the decision steps. The software installationprogram remains in a decision loop until the installation softwareprogram receives, from either of the decision steps 324 or 328, anaffirmative response. However, should the software installation programreceive an affirmative response from a slide not moving 332 decisionstep, the installation software program directs the robotic assembly 214to return the HSA 128 to the nest position 210 and displays a message ona display 334 for the operator to resolve the conflict and restart theprocess at main decision now 300.

FIG. 13 shows the analyze force and position data-decision flow 340 ofthe installation software program utilized by the installation softwareprogram to measure and analyze forces and positions encountered by theHSA 128 while engaging the tolerance ring 176, as the robotic assemblypresses the HSA 128 into the basedeck assembly 168. A start step 342 isthe first installation software program step of the analyze force andposition data-decision flow 340. The software installation programincorporates a force to distance ratio equation 344 to monitorinstallation of the HSA 128 onto (the tolerance ring. During theinstallation process, process parameter measurements representing forceand distance are gathered by the head stack installation tool 204 (ofFIG. 7) and electronically communicated to the computer 206 (of FIG. 7).The computer 206 manipulates the measurements by converting themeasurements into values and substituting those values into equation344. The resulting calculated value, a slope, is compared topredetermined value dynamic slope V of decision step 348.

Turning to FIG. 14, the predetermined value V is empirically derived forforces typically encountered by the HSA 128 while being pressed onto thetolerance ring 176 at specific increments of distance encountered by theHSA 128 while traveling along the tolerance ring 176 and found to have amaximum value of 600, 358. The software also monitors mechanicalresistance encountered during the process at time intervals of aboutevery 50 milliseconds over the distance traveled by the HSA 128 whiletraveled along the tolerance ring 176. Empirically gathered mechanicalresistance data yielded a mechanical resistance as a function ofposition (f(p)) curve 360. The mechanical resistance as a function ofposition curve 360 was arrived at through normal curve fittingtechniques, relating the mechanical resistance encountered by the HSA128 while being pressed onto the tolerance ring 176 to a pointrepresenting the distance covered by the head stack assembly at thepoint in time the mechanical resistance was encountered. A tolerance ofabout plus and minus 5% of the mechanical resistance encountered by theHSA 128 in any region of the tolerance ring 176 was elected and appliedto the force curve resulting in a family of values representing dynamicforce thresholds 362 against which actual measured process data can bedynamically compared. Forces encountered that fall outside the dynamic,either insufficient or excessive, trigger the head stack assemblyinstallation station to abort the process.

Returning to FIG. 13, the equation (F=f(p)+/−x) and slope<V of 348 isinterpreted to mean as follows: should the force (F) measured asencountered by the HSA 128 at a position (p) while being pressed ontothe tolerance ring 176 fall outside the empirically derived force as afunction of position (f(p)) curve, plus or minus (x), about 5% of theforce empirically found to be encountered at position (p) along thetolerance ring 176 during the mating process, the process will beaborted. And, should the force (F) measured as encountered by the HSA128 at a position (p) while being pressed onto the tolerance ring 176fall within the empirically derived mechanical resistance as a functionof position (f(p)) curve 360 (of FIG. 14), plus or minus (x), about 5%of the mechanical resistance empirically found to be encountered atposition (p) along the tolerance ring 176 during the mating process, butthe slope exceeds a predetermined value, empirically found to be about600 the process will be aborted. Or, if the resultant calculated valuefalls outside the predetermined value V, the installation softwareprogram instructs the head stack installation tool 204 to abort theprocess, return the HSA 128 to the nest position 210 (of FIG. 7), anddisplay a message on the display 334 reporting the status of the processand instructing the operator to remove the HSA 128 from the nestposition 112, place the next HSA 128 into the nest position 112 andrestart the process at process step 300. However, typically the softwareinstallation program remains in decision loops until the installationsoftware program receives, from either of the installation softwareprogram steps 346 or 348, an affirmative response.

Upon receipt of an affirmative response from either installationsoftware program steps 346 or 348, the installation software programproceeds to evaluate a course of action to be followed by the head stackinstallation tool 204, based on decision steps represented byinstallation software program steps 350, 352, 354 and 356. In each ofthe four installation software program steps 350, 352, 354 and 356 theinstallation software program checks process end points for specificvalues of force or distance encountered by the HSA 128 during theinstallation process. If the process end point values for the amount offorce encountered by the HSA 128 is less than 11.34 kilograms, butgreater than 0.363 kilograms, and the distance traveled by the HSA 128after encountering the head stack assembly post 174 (of FIG. 4) isgreater than Z minus 0.0254 centimeters, but less than Z plus 0.0254centimeters (where Z is typically between 1.203 centimeters and 3.094centimeters), the head stack installation tool 204 has successfullyinstalled the HSA 128 into the HDA 162 (of FIG. 1). If the process endpoint values for the amount of force encountered by the HSA 128 or thedistance traveled by the HSA 128 after encountering the head stackassembly post 174 falls outside those parameters, the installationsoftware program instructs the head stack installation tool 204 to abortthe installation process attempt, directs the robotic assembly 214 toreturn the HSA 128 to the nest position 210 and displays a message on adisplay 334 for the operator to resolve the conflict and restart theprocess at main decision flow 300.

The present invention provides a head stack assembly installation system(such as 200) with a head stack installation tool (such as 204)electronically communicating with a computer (such as 206) that has anactive installation software program directing and controlling processsteps enacted by head stack installation tool to install a head stackassembly (such as 128) into a head disc assembly of a disc drive (suchas 100). The head stack installation tool provides a nesting position(such as 210) for aligning in staging head stack assembly prior toinstallation into the head disc assembly, an installation position (suchas 212) for locating in securing the head disc assembly while awaitinginstallation of the head stack assembly, a robotic assembly (such as214) the robotic assembly includes an end effector assembly (such as232) supported by a vertical slide assembly (such as 234), which is inturn supported by a horizontal slide assembly (such as 236) thatattaches to a main plate (such as 208). A measurement assembly made upof a communications interface electronics assembly (such as 246)electronically communicating with a radial displacement potentiometer(such as 248), a linear variable differential transformer (such as 250),and a load cell (such as 252). The robotic assembly picks and places thehead stack assembly into the head disc and the measurement assemblycollects and communicates process position and force parameters to thecomputer for use by the computer in calculating distance and force data.The active installation software program directs and controls enactmentof process steps followed by the head stack installation tool bydirecting the computer to execute installation software program stepsbased on the position and force data calculated by the computer.

It is clear that the present invention is well adapted to attain theends and advantages mentioned as well as those inherent therein. While apresently preferred embodiment of the invention has been described forpurposes of the disclosure, it will be understood that numerous changescan be made which will readily suggest themselves to those skilled inthe art. Such changes are encompassed within the spirit of the inventiondisclosed and as defined in the appended claims.

1. A head stack assembly installation system comprising: a frame; a headstack installation tool supported by the frame, comprising: a roboticassembly for picking and pressing a head stack assembly within a headdisc assembly; and a measurement assembly for measuring process positionand force parameters encountered by the head stack assembly duringinstallation of the head stack assembly within the head disc assembly;and a computer electronically communicating with the head stackinstallation tool for directing and controlling the robotic assemblyduring installation of the head stack assembly based on position andforce parameter measurements from the measurement assembly.
 2. The headstack assembly installation system of claim 1, in which the head stackinstallation tool comprises: a main plate having a nesting position andan installation position, the main plate supporting the roboticassembly, the nesting position for aligning the head stack assembly, theinstallation position for aligning the head disc assembly; a head stackassembly scanner for identifying the head stack assembly andcommunicating the identification to the computer; a head disc assemblyscanner for identifying the head disc assembly and communicating theidentification to the computer; a plurality of head stack assemblyalignment pins for aligning an actuator body and a voice coil assemblyof the head stack assembly; and a connector nest for aligning a flexconnector body relative to the voice coil assembly of the head stackassembly.
 3. The head stack assembly installation system of claim 2wherein the robotic assembly comprises: a horizontal slide assemblyattached to the main plate; a vertical slide assembly supported andselectively positioned horizontally by the horizontal slide assembly; anend effector assembly supported and selectively positioned vertically bythe vertical slide assembly; a horizontal slide sensor detecting andcommunicating end effector assembly horizontal position to the computer;and a vertical slide sensor detecting and communicating end effectorassembly vertical position to thc computer.
 4. The head stack assemblyinstallation system of claim 3, in which the end effector assemblycomprises: radially disposed positionable gripper sections configuredfor communication with a beveled pick and place member of the head stackassembly; and a pair of opposing positionable flex connector grippersconfigured for communication with the flex connector body of the headstack assembly.
 5. The head stack assembly installation system of claim4, in which the measurement assembly comprises: a potentiometersupported by the end effector assembly for reporting radial displacementmeasurements of the radially disposed positionable gripper sectionsrelative to the beveled pick and place member to the computer; a linearvariable differential transformer supported by the vertical slideassembly for reporting vertical distance measurements traveled by thehead stack assembly relative to the tolerance ring to the computer; anda load cell supported by the end effector assembly for reportingmechanical resistance between the head stack assembly and the tolerancering to the computer.
 6. The head stack assembly installation system ofclaim 5 wherein the computer comprises: a central processing unitcommunicating with a installation software program; a volatile memory incommunication with the central processing unit for temporarily storingthe installation software program, the identity of the head stackassembly provided by the head stack assembly scanner, the identity ofhead disc assembly provided by the head disc assembly, and measurementsfrom the load cell, the linear variable differential transformer, thepotentiometer, the vertical slide sensor and the horizontal slidesensor; a head stack assembly data base in communication with thecentral processing unit and storing physical characteristics of all headstack assemblies available for installation; and a head disc assemblydata base in communication with the central processing unit and storingphysical characteristics of all head disc assemblies available toreceive head stack assemblies.
 7. The head stack assembly installationsystem of claim 6 wherein the head stack installation station furthercomprises a communication interface electronics assembly communicatingwith the computer providing communication interface between the computerand the head stack installation tool, the measurement assembly and therobotic assembly.